DETRITAL-ZIRCON AGES OF UPPER MISSISSIPPIAN–LOWER PENNSYLVANIAN DEPOSITS INDICATE MORROWAN INCEPTION OF THE ANCESTRAL ROCKY MOUNTAINS OROGEN
LAWTON, Timothy, University of Texas at Austin, Bureau of Economic Geology, 10611 Exploration Way, Austin, TX 78758, THOMAS, William, Emeritus University of Kentucky, Geological Survey of Alabama, P.O. Box 869999, Tuscaloosa, AL 35486-6999 and GEHRELS, George E., Department of Geosciences, University of Arizona, Tucson, AZ 85721